CourseMarket

Modern microservices-based e-commerce platform for online courses. This repository demonstrates end-to-end architecture with identity, API gateway, domain-driven ordering, messaging, and a server-rendered web frontend.

Features

• Identity & Authorization: Duende IdentityServer with OAuth2/OIDC, Resource Owner Password and Client Credentials flows, refresh tokens, role claims
• API Gateway: Ocelot for routing/aggregation, JWT validation, and RFC 8693 Token Exchange
• Microservices: Catalog (MongoDB), Basket (Redis), Discount (PostgreSQL), Order (SQL Server, DDD), PhotoStock, FakePayment
• Messaging: MassTransit + RabbitMQ for event-driven communication (e.g., course-name-changed, create-order)
• Web Application: ASP.NET Core MVC + Razor Views, cookie auth, OpenIdConnect token management, FluentValidation
• Operability: Docker Compose to orchestrate services; Swagger for service contracts

Architecture Overview

• Frontend (Frontends/CourseMarket.Web): MVC, HttpClient + delegating handlers, calls services via the API gateway
• API Gateway (Gateways/CourseMarket.Gateways.Web): Ocelot, TokenExchangeDelegateHandler for token exchange and JWT validation
• Identity (IdentityServer/CourseMarket.IdentityServer): ApiResource/Scope/Client configuration and user management
• Services (Services/*): Independent microservices with their own storage and contracts
  • Catalog: MongoDB, JWT-protected REST API
  • Basket: Redis, MassTransit consumer, JWT authorization
  • Discount: PostgreSQL, JWT authorization
  • Order: DDD (Domain, Application, Infrastructure), EF Core + SQL Server, MediatR, MassTransit consumers
  • PhotoStock: File/image operations
  • FakePayment: Simulated payment workflow
• Shared (Shared/CourseMarket.Shared): Shared DTOs, messages, and utilities

Key Technical Decisions and Patterns

• Identity: IdentityServer with ApiResource/ApiScope/Client configuration; ROPC for user flow, Client Credentials for service-to-service access
• Gateway: Ocelot as a single entry point; TokenExchangeDelegateHandler to securely call discount and payment services via token exchange
• DDD (Order Service):
  • Domain: Order, OrderItem, Address, IAggregateRoot, Entity abstractions
  • Application: AutoMapper profiles, MediatR commands/handlers, message consumers
  • Infrastructure: EF Core, migrations, SQL Server connection, and OrderDbContext
• Messaging: MassTransit with RabbitMQ; queues/endpoints for course-name-changed and create-order
• Data Access: Catalog (MongoDB), Basket (Redis), Discount (PostgreSQL), Order (SQL Server)
• Validation: FluentValidation for view model validation
• HttpClient Factory: Typed service proxies with delegating handlers to inject access tokens

Technologies

• .NET 5 / ASP.NET Core, MVC/Razor
• Duende IdentityServer, Duende IdentityModel
• Ocelot API Gateway
• MassTransit, RabbitMQ
• Entity Framework Core (SQL Server), MongoDB Driver, Npgsql (PostgreSQL), StackExchange.Redis
• MediatR, AutoMapper, FluentValidation, Swashbuckle (Swagger)
• Docker / Docker Compose

Service Topology and Databases

• Catalog: MongoDB (catalogdb)
• Basket: Redis (basketdb)
• Discount: PostgreSQL (discountdb)
• Identity & Order: SQL Server (identitydb, orderdb)
• Messaging: RabbitMQ (rabbitmq:management)

Identity and Authorization

IdentityServer Config.cs summary:

• ApiResources: resource_catalog, resource_basket, resource_discount, resource_order, resource_payment, resource_photo_stock, resource_gatewayweb
• Scopes: *_fullpermission, gatewayweb_fullpermission, IdentityServerConstants.LocalApi
• Clients:
  • WebMvcClient (Client Credentials)
  • WebMvcClientForUser (ROPC, offline access, refresh tokens)
  • TokenExchangeClient (Token Exchange grant)

Frontend uses Cookie Authentication; service calls use ClientCredentialTokenHandler and ResourceOwnerPasswordTokenHandler to attach tokens.

Messaging Examples

• Basket Service: course-name-changed-event-basket-service queue, CourseNameChangedEventConsumer
• Order Service: create-order-service and course-name-changed-event-order-service queues, corresponding consumers

Folder Structure (Overview)

• Frontends/CourseMarket.Web: MVC app, Startup.cs, service proxies
• Gateways/CourseMarket.Gateways.Web: Ocelot configuration, token exchange handler
• IdentityServer/CourseMarket.IdentityServer: IdentityServer configs and UI
• Services/*: Independent microservices and layered architecture (notably Order)
• Shared/CourseMarket.Shared: Shared DTOs/messages and helpers

Run with Docker Compose

Prerequisite: Docker Desktop

# Run from repository root
docker compose up --build -d

Components and ports are built from the docker-compose file. On first run, seed/migrations are applied automatically by the services (e.g., Order API calls Database.Migrate).

For local development you can also run services individually (VS/VS Code F5). Update connection strings and IdentityServerUrl values in the corresponding appsettings.Development.json files.

Development Notes

• Order API: MediatR command handlers, EF Core migration pipeline, DbContext configuration
• Catalog API: JWT audience validation (resource_catalog), AutoMapper, Mongo DatabaseSettings
• Basket API: RedisService singleton, MassTransit hosted service, audience resource_basket
• Frontend: FluentValidation, cookie auth and token management, HttpClient via API Gateway

Why This Project?

• Demonstrates microservices end-to-end: identity, gateway, messaging, polyglot persistence, DDD, and layered architecture
• Mirrors real-world scenarios: course rename events, basket updates, order creation, and payment workflow

Roadmap (Optional)

• Observability: Health Checks, OpenTelemetry, centralized logs/metrics
• Resilience: Polly retry, Circuit Breaker
• Deployment: Kubernetes manifests/Helm charts
• UI: Modern SPA (React/Angular/Vue) alongside MVC

---

This repository highlights my professional skills across microservices, identity, and messaging in .NET. Feel free to open issues for questions or feedback.